POTENTIAL GAIN FROM INCLUDING MAJOR GENE INFORMATION IN BREEDING VALUE ESTIMATION

Two indexes were compared for the selection of a quantitative trait in the case of a mixed inheritance. The first index did not consider the major genotype information (standard method) whereas the second index took this information into account (modified method). Two types of se lection scheme were considered: individual selection and selection bas ed on a progeny test. The model for the estimation of genetic progress and evolution of allele frequencies takes overlapping generations int o account. All of the effects studied suggested a large number of inte ractions. However, it can be concluded that information about the majo r gene should be put into the selection indexes when the heritability is low, the major gene effect high and its initial frequency small, in particular for a recessive major gene. The selection pressure has lit tle influence on the results. In the short term, the modified method i s of more value in the case of individual selection than in the case o f selection based on a progeny test. On the whole, the extra genetic g ain of the modified method is limited and considering the major genoty pes in the selection indexes without any change of the selection schem e is probably not the best way to use this information.